 Growth factor (biology)

A biological growth factor is a signaling ligand that modulates cell growth, cell proliferation, cell differentiation or cell survival. Many are proteins recognized by cell-surface receptors. The resulting response depends on which receptors and intracellular pathways the target cell contains.

For example, epidermal growth factor engages the epidermal growth factor receptor, while FGF8 acts through FGF receptors. These interactions can alter gene expression through signal transduction. The ligand and its receptor are separate molecular components, so their distribution jointly determines where a signal can act.^[ref]